Sexual Disorder Agents

Sexual disorder agents

Sildenafil (Viagra)

Phosphodiesterase type 5 inhibitor

(PDE5 inhibitor)

• Erectile dysfunction

• Pulmonary hypertension

• Benign prostatic hyperplasia (tadalafil only)

• PDE5 inhibition → ↓ breakdown of cGMP → ↑ cGMP → ↑ smooth muscle relaxation in reaction to nitric oxide activation → pulmonary vasodilation, penile smooth muscle relaxation, and increased blood flow

• Decrease in pulmonary vascular resistance

• ↑ Blood flow in the corpus cavernosum → increase in penis size during an erection

• Known hypersensitivity to sildenafil or any ingredient in the formulation. 

• Concomitant use of organic nitrates or nitrites. [ref] Concomitant use of riociguat. 

• Do not use for treatment of ED in men for whom sexual activity is inadvisable because of underlying cardiovascular status. 

ED: Headache, flushing, dyspepsia/heartburn. 

PAH: Headache, dyspepsia,  flushing, epistaxis, insomnia, exacerbated dyspnea,  diarrhea, myalgia,  erythema,  pyrexia. 

• Headaches, cutaneous flushing

• Lightheadedness

• Sildenafil: visual deficits (blue-tinted vision, or cyanopia) due to PDE-6 inhibition in the retina [6]

• Runny nose, nasal congestion

• Exanthema

• Dyspepsia

• Rarely: myocardial infarction, stroke, hearing loss, optic neuropathy

• Nitrates: Use of PDE5 inhibitors with nitrates (e.g., nitroglycerin) can result in life-threatening hypotension.

  • Both nitrates (e.g., sublingual nitroglycerin) and PDE-5 inhibitors (e.g., vardenafil) function by increasing cGMP concentration → activation of myosin light chain phosphatase (MLCP) → dephosphorylation of light chains of myosin → smooth muscle cell relaxation in blood vessels → vasodilation

• Alpha blockers: Use of PDE5 inhibitors with alpha blockers can also result in hypotension.

Patients being treated with PDE5s should not receive nitrates in unstable angina pectoris, acute coronary syndrome, or myocardial infarction because this could result in a life-threatening decrease in blood pressure!